Certain types of bacteria in water are harmful to marine life. to determine how to eliminate two different types of harmful bacteria found in the local waterways, a marine biologist is going to test three different treatments using a control group. Why should the biologist use a block design?
a. to account for unknown variables
b. there are different types of marine life in the water
c. the different types of bacteria may respond differently to the treatments
d. the treatments may also harm good bacteria